OK, some atomic basics before we get into nuclear reactions. I've covered a bit of the basics regarding radiation, which is a byproduct of an unstable atom going stable. Let me cover basic atomic structures so that I can get into nuclear fission in the next installment. The nucleus, or center, of an atom is where the atomic magic occurs. The nucleus is composed of protons, which have a positive charge, and neutron which have no charge at all. Both protons and neutrons are call nuclides since they reside in the nucleus of each atom. The number of protons in an atomic nucleus is called the atomic number, while the total number of nuclides in a nucleus (protons + neutrons) is called the mass number.The force that holds nuclides together is one that none of us have any experience with - the nuclear force. It is extremely powerful but only works on a small scale. Other forces like gravity and electrostatic forces we do have experience with as we see them in the macroscopic world that we exist in. The nuclear force must be very strong since protons have a positive charge and would therefore repel each other. So a much stronger force is present that clumps them together.
Now, most stable atoms have the same number of positively charged protons in the nucleus, and negatively charged electrons in orbit. If not, then the atom is said to be ionized. Also, there is a balance between protons and neutrons, but it is not 1-to-1. There are slightly more neutrons than protons in bigger atoms and that increases as the atomic number goes up. When that gets out of balance due to relatively too many neutrons, the atom is an isotope. Isotopes are the different versions of the same atom with the same number of protons but different number of neutrons. Not all isotopes are unstable. Some are actually stable and remain in that state. It is the unstable isotopes that are radioactive - giving off radiation in various forms to become stable again. For example, hydrogen, denoted in the periodic table by H, has two stable isotopes, H-1 and H-2. H-2 has two nulides (one proton, one neutron) but is stable. Stable isotopes sometimes have names. H-2 is called deuterium (also designated as D-2). Another hydrogen isotope, H-3, is unstable (thus radioactive) and is called tritium (isn't that the stuff Dr. Octopus was using to form a miniature self-sustained fusion reaction in Spiderman 2?).
Some isotopes of certain elements are extremely common in nature. Uranium is one of those as there are three isotopes: U-238, U-235, and U-234 (and yes, that's a lot of protons and neutrons in each). U-238 is the most common, comprising 99.2745% of all uranium. U-235 comes in a distant second at 0.72%, while U-234 comes in dead last at a trace 0.0055%. Each of these isotopes have unique nuclear properties, but it is U-235 that is most important to nuclear applications, both for power generation and for nuclear weapons. But that's another story. Ready for a quiz now? Here are some common isotopes:
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